Methods and apparatus for water injection in a turbine engine

ABSTRACT

Methods and apparatus for injecting water into a turbine engine are described. In one embodiment, water injection apparatus is provided for injecting water into the gas flow through the engine, e.g., at a high pressure and/or low pressure compressor inlet. The water injection apparatus includes a plurality of nozzles arranged so that water injected into the gas flow by the nozzles results in substantially uniformly reducing the temperature of the gas flow at the high pressure compressor outlet.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/094,094, filed Jul. 24, 1998.

BACKGROUND OF THE INVENTION

[0002] This invention relates generally to gas turbine engines and moreparticularly, to prebooster and precompressor water injection in a gasturbine engine.

[0003] Gas turbine engines typically include a compressor forcompressing a working fluid, such as air. The compressed air is injectedinto a combustor which heats the fluid causing it to expand, and theexpanded fluid is forced through a turbine. The compressor typicallyincludes a low pressure compressor and a high pressure compressor.

[0004] The output of known gas turbine engines may be limited by thetemperature of the working fluid at the output of the high pressurecompressor, sometimes referred to as temperature “T3”, and by thetemperature of the working fluid in the combustor outlet, sometimesreferred to as temperature “T41”. To reduce both the T3 and T41temperatures, it is known to use an intercooler positioned in the fluidflow path between the low pressure compressor and the high pressurecompressor. In steady state operation, the intercooler extracts heatfrom the air compressed in the low pressure compressor, which reducesboth the temperature and volume of air entering the high pressurecompressor. Such reduction in temperature reduces both the T3 and T41temperatures. Increased power output therefore can be achieved byincreasing flow through the compressor.

[0005] Typically, cool water or air circulates through the intercooler,and heat is transferred from the air flow to the cool water or air. Thewater or air absorbs the heat, and the heated water or air is thenremoved. Removing the heated water or air results in losses in totalcycle thermal efficiency. Therefore, although an intercooler facilitatesincreased power output, the intercooler reduces thermal efficiency ofthe engine. The intercooler also introduces pressure losses associatedwith the removal of air, the actual cooling of that air, and ducting thecooled air to the compressor. Further, it is impractical for anintercooler to also provide interstage cooling.

[0006] With at least some known intercoolers, the heated water isremoved using a water cooler which dissipates the heated water through acooling tower as vapor into the environment. Of course, releasing thevapor into the environment raises environmental concerns. Also, asignificant amount of water is required by such intercoolers, and suchhigh water consumption increases the operational costs.

[0007] It would be desirable to provide a partial increased power outputas achieved with intercoolers yet also provide improved thermalefficiency as compared to at least known intercoolers. It also would bedesirable to provide increased power output even for single rotor gasturbines.

SUMMARY OF THE INVENTION

[0008] These and other objects may be attained by a gas turbine engineincluding prebooster or precompressor water injection which providesmany of the same advantages, yet overcomes some shortcomings, ofintercooling. In an exemplary embodiment, a gas turbine engine suitablefor use in connection with water spray injection includes a low pressurecompressor, a high pressure compressor, and a combustor. The engine alsoincludes a high pressure turbine, a low pressure turbine, and/or a powerturbine. A water injection apparatus is provided for injecting waterinto an inlet of the high pressure compressor. The water spray injectionapparatus is in flow communication with a water supply, and duringengine operation, water is delivered from such supply through theinjection apparatus to the inlet of the compressor.

[0009] In operation, air flows through the low pressure compressor, andcompressed air is supplied from the low pressure compressor to the highpressure compressor. In addition, a water spray is supplied to the inletof the high pressure compressor, and the water spray enters into thehigh pressure compressor through the inlet. Due to the high temperatureenvironment at the location at which the water spray is injected, thewater spray partially evaporates before entering the high pressurecompressor. The water spray cools the air flow in the high pressurecompressor for at least each stage of compression through which suchspray flows, i.e., until it evaporates. Usually about by the mid-stagesof the high pressure compressor, and depending on the water quantity,the majority of the water spray is evaporated.

[0010] The air and water vapor is further compressed by the highpressure compressor, and the highly compressed air is delivered to thecombustor. Airflow from the combustor drives the high pressure turbine,the low pressure turbine, and the power turbine. Waste heat is capturedby boilers, and heat from the boilers in the form of steam may bedelivered to upstream components.

[0011] The water spray provides an advantage in that the temperature ofthe airflow at the outlet of the high pressure compressor (temperatureT3) and the temperature of the airflow at the outlet of the combustor(temperature T41) are reduced in steady state operations as compared tosuch temperatures without the spray. Specifically, the water sprayextracts heat from the hot air flowing into and through the highpressure compressor, and by extracting such heat from the air flow, theT3 and T41 temperatures are reduced and compressive horsepower isreduced. The heat is removed as the water vaporizes. Reducing the T3 andT41 temperatures provides the advantage that the engine is not T3 andT41 constrained, and therefore, the engine may operate at higher outputlevels than is possible without such water spray. That is, with theabove described water spray injection and using the same high pressurecompressor discharge temperature control limit, the high pressurecompressor can pump more air which results in a higher pressure ratioand a higher output.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a schematic illustration of a gas turbine engineincluding compressor water injection in accordance with one embodimentof the present invention;

[0013]FIG. 2 is a schematic illustration of a gas turbine engineincluding compressor water injection and intercooling in accordance withanother embodiment of the present invention;

[0014]FIG. 3 is a schematic illustration of a gas turbine engineincluding booster water injection in accordance with one embodiment ofthe present invention;

[0015]FIG. 4 is a schematic illustration of a single rotor gas turbineengine including compressor water injection in accordance with anotherembodiment of the present invention;

[0016]FIG. 5 is a schematic illustration of a gas turbine engineincluding booster and compressor water injection in accordance withstill yet another embodiment of the present invention;

[0017]FIG. 6 is a schematic illustration of a gas turbine engineincluding compressor water injection in accordance with yet anotherembodiment of the present invention;

[0018]FIG. 7 is a schematic illustration of the gas turbine engine shownin FIG. 6 coupled to an electric generator;

[0019]FIG. 8 is a side view of an LM6000 engine of General ElectricCompany modified to include spray injection;

[0020]FIG. 9 is a perspective view of a connector for connecting theeight stage bleed of the engine shown in FIG. 8 to an air manifold;

[0021]FIG. 10 is a cross sectional view of the engine shown in FIG. 8and illustrating a nozzle configuration;

[0022]FIG. 11 is a side view of a nozzle;

[0023]FIG. 12 is a top view of the nozzle shown in FIG. 11;

[0024]FIG. 13 is a schematic diagram of a control circuit forcontrolling the supply of water and air to the nozzles in the engineshown in FIG. 8;

[0025]FIG. 14 is a chart illustrating an exemplary water schedule forthe engine arrangement illustrated in FIG. 8;

[0026]FIG. 15 is a chart illustrating the output, heat rate, flow, andwater supplied to the engine illustrated in FIG. 8 at various ambienttemperatures;

[0027]FIG. 16 is a chart illustrating the high pressure turbine cavityflow relationship versus the high pressure compressor exit correctedspeed of the engine illustrated in FIG. 8;

[0028]FIG. 17 is a table showing the results for pressure and airatomized nozzle operation;

[0029]FIG. 18 is a graphical representation of water flow versus highpressure compressor evaporation; and

[0030]FIG. 19 is a table showing the effect of nozzle performance onevaporation in the high pressure compressor.

DETAILED DESCRIPTION

[0031] Set forth below are exemplary configurations of water sprayinjection in accordance with various embodiments of the presentinvention. Initially, it should be understood that although specificimplementations are illustrated and described, water spray injection canbe practiced using many alternative structures and in a wide variety ofengines. In addition, and as described below in more detail, water sprayinjection can be performed at the inlet of a high pressure compressor,at an inlet of the booster, or at both locations.

[0032] Water spray injection provides many of the same advantages ofintercooling yet overcomes some shortcomings of intercooling. Forexample, and with intercooling, the heated water (or air) is removed andremoval of such heated water (or air) reduces the thermal efficiency ofthe cycle as well as creates environmental concerns. The significantpower increase provided by intercooling typically overcomes theshortcomings associated with intercooling and as a result, intercoolingoften is utilized when extra power is required using a different orlarger airflow booster and a larger high pressure turbine flow function.Water spray injection, as described below, provides a power increasewhich may be somewhat less than the maximum power increase provided in asimilarly situated intercooler. With water spray injection, however, farless water is utilized and water exits the cycle as water vapor atexhaust gas temperature.

[0033] Referring now specifically to the drawings, FIG. 1 is a schematicillustration of a gas turbine engine 10 which, as is well known,includes a low pressure compressor 12, a high pressure compressor 14,and a combustor 16. Engine 10 also includes a high pressure turbine 18,a low pressure turbine 20, and a power turbine 22. Engine 10 furtherincludes a water injection apparatus 24 for injecting water into aninlet 26 of high pressure compressor 14. Further details regarding waterinjection apparatus 22 are set forth below. For purposes of FIG. 1,however, it should be understood that apparatus 24 is in flowcommunication with a water supply (not shown) and water is deliveredfrom such supply through apparatus 24 to inlet 26 of compressor 14.Apparatus 24 is air aspirated using a bleed source off compressor 14 toprovide a finer spray mist. Waste heat boilers 28, 30, and 32 arelocated downstream of power turbine 22. As is known in the art, feedwater is supplied to boilers 28, 30, and 32 via a feedwater line 34, andwater in the form of steam is communicated from boilers 28, 30, and 32to various upstream components. Particularly, steam from boiler 28 isprovided to an inlet 36 of combustor 16, steam from boiler 30 isprovided to an inlet of low pressure turbine 20 and an inlet of powerturbine 22, and steam from boiler 32 is provided to a last stage ofpower turbine 22. Except for water spray injection apparatus 24, thevarious components of turbine 10 are known in the art.

[0034] In operation, air flows through low pressure compressor 12, andcompressed air is supplied from low pressure compressor 12 to highpressure compressor 14. In addition, a water spray is supplied to inlet26 of high pressure compressor 14, and the water spray enters intocompressor 14 through inlet 26. Due to the high temperature environmentat the location at which the water spray is injected, the water spraypartially evaporates before entering high pressure compressor 14. Thewater spray cools the air flow in high pressure compressor 14 for atleast each stage of compressor 14 through which such spray flows, i.e.,until it evaporates. Usually by the sixth stage of compressor 14, thewater spray is totally evaporated.

[0035] The air is further compressed by high pressure compressor 14, andhighly compressed air is delivered to combustor 16. Airflow fromcombustor 16 drives high pressure turbine 18, low pressure turbine 20,and power turbine 22. Waste heat is captured by boilers 28, 30, and 32,and the waste heat steam is delivered to upstream components coupled toboilers 28, 30 and 32 as described above.

[0036] The water particles from water spray apparatus 24 provide theadvantage that the temperature of the airflow at the outlet of highpressure compressor 14 (temperature T3) and the temperature of theairflow at the outlet of combustor 16 (temperature T41) are reduced ascompared to such temperatures without the spray. Specifically, the waterspray extracts heat from the hot air flowing into and through compressor14, and by extracting such heat from the air flow, the T3 and T41temperatures are reduced along with the required compressor power.Reducing the T3 and T41 temperatures provides the advantage that engine10 is not T3 and T41 constrained, and therefore, engine 10 may operateat higher output levels by throttle pushing than is possible withoutsuch water spray. In addition to increased power output, water sprayinjection as described above provides the advantage of less waterconsumption as compared to intercooling under the same conditions.

[0037]FIG. 2 is a schematic illustration of another embodiment of a gasturbine engine 50 including water spray injection. Engine 50 includes alow pressure compressor 52, a high pressure compressor 54, and acombustor 56. Engine 50 also includes a high pressure turbine 58, alower pressure turbine 60, and a power turbine 62. Engine 50 furtherincludes a water injection apparatus 64 for injecting water into aninlet 66 of high pressure compressor 54. For purposes of FIG. 2, itshould be understood that apparatus 64 is in flow communication with awater supply (not shown) and water is delivered from such supply throughapparatus 64 to inlet 66 of compressor 54. An intercooler 68 also ispositioned in series flow relationship with booster 52 to receive atleast a portion or all of the air flow output by booster 52, and theoutput of intercooler 68 is coupled to inlet 66 of compressor 54. Ofcourse, cooling water is supplied to intercooler 68 as illustrated orblower fans could be used for air cooling. Intercooler 68 could, forexample, be one of the intercoolers described in U.S. Pat. No.4,949,544.

[0038] Waste heat boilers 70, 72, and 74 are located downstream of powerturbine 62. As is known in the art, feed water is supplied to boilers70, 72, and 74 via a feedwater line 76 which extends through a firststage 78A of intercooler 68, and steam is communicated from boilers 70,72, and 74 to various upstream components. Particularly, steam fromboiler 70 is provided to an inlet 80 of combustor 56, steam from boiler72 is provided to an inlet of low pressure turbine 60 and an inlet ofpower turbine 62, and steam from boiler 74 is provided to a last stageof power turbine 62. Except for water spray injection apparatus 64, thevarious components of turbine 50 are known in the art.

[0039] In operation, air flows through low pressure compressor 52, andcompressed air is supplied from low pressure compressor 52 to highpressure compressor 54. At least some or all compressed air from lowpressure compressor 52 is diverted to flow through a second stage 78B ofintercooler 68, and such diverted air is cooled and supplied to inlet 66of high pressure compressor 54. In addition, a water spray is suppliedto inlet 66 of high pressure compressor 54, and the water spray entersinto compressor 54 through inlet 66. Due to the higher temperatureenvironment at the location at which the water spray is injected, thewater spray partially evaporates before entering high pressurecompressor 54. The water spray cools the air flow in high pressurecompressor 54 for at least each stage of compressor 54 through whichsuch spray flows, i.e., until it evaporates. Usually by the sixth stageof compressor 54, the water spray is evaporated.

[0040] The air is further compressed by high pressure compressor 54, andhighly compressed air is delivered to combustor 56. Airflow fromcombustor 56 drives high pressure turbine 58, low pressure turbine 60,and power turbine 62. Waste heat is captured by boilers 70, 72, and 74,and the waste heat as steam is delivered to upstream components coupledto boilers 70, 72, and 74 as described above.

[0041] By providing a combination of intercooling and water sprayinjection, it is believed that increased power output is provided byengine 50 as compared to engine 10. Intercooler 68 could take the flowfield into the compressor down in temperature to where condensate couldappear from ambient humidity. The water spray then could be added intocompressor 54 to further reduce T3 at its exit along with reducing itspower required to run. However, engine 50 requires more water ascompared to engine 10, and engine 50 does dissipate some water to theenvironment, due to operation of intercooler 68 along with theadditional water spray exiting the stack as a vapor at exhaust stacktemperature. As compared to the results obtained if only intercooling isused to achieve a power output of engine 50, however, the combination ofwater spray injection and intercooling results in more waterconsumption.

[0042] Although not shown in the exemplary configuration set forth inFIG. 2, it is contemplated that rather than, or in addition to, waterspray injection at inlet 66 of high pressure compressor 54, suchinjection can be performed at the inlet of low pressure compressor, orbooster, 52 (booster water spray injection is illustrated in FIG. 3).Similar advantages in the decrease of T3 and T41 temperatures may beachieved by such injection.

[0043] An exemplary configuration of an engine 82 including boosterwater spray injection is set forth in FIG. 3. The configuration ofengine 82 is substantially similar to engine 10 shown in FIG. 1 with theexception that water spray injection apparatus 24 is located at an inlet38 of low pressure compressor, or booster, 12. In engine 82, water isinjected into booster 12 and cools the air flowing through booster 12.Cooling the air flow through booster 12 provides the advantages ofdecreasing T3 and T41 temperatures as described above. Only about 1%water spray can be injected into booster 12, which water will evaporateby the end of the booster.

[0044]FIG. 4 is a schematic illustration of a single rotor gas turbineengine 84 including compressor water injection in accordance withanother embodiment of the present invention. Engine 84 includes a highpressure compressor 86, a combustor 88, and a high pressure turbine 90.A shaft 92 coupled high pressure compressor 86 and high pressure turbine90. A power turbine 94 is downstream from high pressure turbine 90, anda shaft 96 is coupled to and extends from power turbine 94. Water sprayinjection apparatus 98 is located at an inlet 100 of high pressurecompressor 86.

[0045] A dual rotor gas turbine engine 10 is shown schematically in FIG.5. Engine 160 includes a booster 162 and a power turbine 164 connectedby a first shaft 166, a high pressure compressor 168 and a high pressureturbine 170 connected by a second shaft 172, and a combustor 174. Engine160 further includes pre-booster water spray injection apparatus 176 andpre-compressor water spray injection apparatus 178.

[0046]FIG. 6 is a schematic illustration of a gas turbine engine 200including compressor water injection in accordance with yet anotherembodiment of the present invention. Engine 200 includes a low pressurecompressor 202 and a high pressure compressor 204. In this embodiment,low pressure compressor 202 is a five stage compressor, and highpressure compressor 204 is a fourteen stage compressor. A combustor (notshown) is downstream from compressor 204. Engine 200 also includes ahigh pressure turbine (not shown) and a low pressure turbine (notshown). The high pressure turbine is a two stage turbine, and the lowpressure turbine is a five stage turbine.

[0047] Engine 200 further includes a water injection apparatus 206 forinjecting water into an inlet 208 of high pressure compressor 204. Waterinjection apparatus 206 includes a water metering valve 210 in flowcommunication with a water manifold 212. Water is supplied to meteringvalve 210 from a water source or reservoir. Air is supplied to an airmanifold 213 from an eight stage bleed 214 of high pressure compressor204. Bleed 214 serves as a source of heated air. A heat exchanger 216 iscoupled to flow pipe or tube 218 which extends from eight stage bleed214 to air manifold 213. Feeder tubes 220 and 221 extend from airmanifold 213 and water manifold 212 to twenty four spray nozzles 222 and223 radially spaced and extending through outer casing 224. Nozzles 222are sometimes referred to herein as short nozzles 222, and nozzles 223are sometimes referred to herein as long nozzles 223. Nozzles 222 and223 are radially spaced around the circumference of casing 224 in analternating arrangement as described below in more detail.

[0048] Twenty four water feeder tubes 221 extend from water manifold212, and twenty four air feeder tubes 220 extend from air manifold 213.Each nozzle 222 is coupled to one water feeder tube 221 from watermanifold 212 and to one air feeder tube 220 from air manifold 213.Generally, water flowing to each nozzle 222 and 223 is atomized usingthe high pressure air (e.g., at about 150 psi) taken off eight stagebleed 214 of high pressure compressor 204. The droplet diameter, in thisembodiment, should be maintained at about 20 microns. Such dropletdiameter is maintained by controlling the rate of flow of water throughvalve 210 using the water schedule described below in more detail andutilizing the high pressure air from bleed 214. Except for water sprayinjection apparatus 206, the various components of engine 200 are knownin the art.

[0049] In operation, engine 200 is operated to its maximum power outputwithout spray injection, i.e., water valve 210 is closed. In this modeof operation, air flows through air pipe 218 to nozzles 222 and 223. Theair is cooled by heat exchanger 216. However, since no water is allowedthrough valve 210, no water is injected into the flow to high pressurecompressor 204.

[0050] Once maximum power output is achieved, water injection apparatusis activated and water flows to nozzles 222 and 223. Heat exchanger 216continues operating to reduce the temperature of the air supplied tonozzles 222 and 223. Particularly, the air flow from the eighth stagebleed 214 typically will be at about 600-650 deg F. To reduce thethermal differential, or mismatch, between the bleed hot air and thewater from the water reservoir, the temperature of the air from theeighth stage bleed 214 is reduced to about 250 deg F. by heat exchanger216 while maintaining the pressure of the air at about 150 psi. Bymaintaining the pressure at about 150 psi, the air has sufficientpressure to atomize the water.

[0051] Nozzles 222 and 223 inject water sprays 226 and 227 (illustratedschematically in FIG. 6) into the flow at inlet 208 of high pressurecompressor 204, and the water spray enters into compressor 204 throughinlet 208. Due to the high temperature environment at the location atwhich the water spray is injected, the water spray partially evaporatesbefore entering high pressure compressor 204. The water spray cools theair flow in high pressure compressor 204 for at least each stage ofcompressor 204 through which such spray flows, i.e., until itevaporates. Usually by the sixth stage of compressor 204, the waterspray is totally evaporated. The air is further compressed by highpressure compressor 204, and highly compressed air is delivered to thecombustor. Airflow from the combustor drives the high pressure turbineand the low pressure turbine.

[0052] The water particles from water spray apparatus 206 provide theadvantage that the temperature of the airflow at the outlet of highpressure compressor 204 (temperature T3) and the temperature of theairflow at the outlet of the combustor (temperature T41) are reduced ascompared to such temperatures without the spray. Specifically, the waterspray extracts heat from the hot air flowing into and through compressor204, and by extracting such heat from the air flow, the T3 and T41temperatures are reduced along with the required compressor power.Reducing the T3 and T41 temperatures provides the advantage that engine200 is not T3 and T41 constrained, and therefore, engine 200 may operateat higher output levels by throttle pushing than is possible withoutsuch water spray.

[0053] That is, by injecting atomized water spray in front of highpressure compressor 204, the inlet temperature of high pressurecompressor 204 is significantly reduced. Therefore, using the samecompressor discharge temperature control limit, high pressure compressor204 is able to pump more air, achieving a higher pressure ratio. Thisresults in higher output and improved efficiency. In addition toincreased power output, water spray injection as described aboveprovides the advantage of less water consumption as compared tointercooling under the same conditions. Rather than the T3 and T41temperature constraints, it should be understood that with the waterspray configuration, the engine constraints may no longer be suchtemperatures, e.g., the constraints may the turbine inlet temperatureT48 of the high pressure turbine and the core speed.

[0054] The above described water injection apparatus 206 may also beutilized in connection with pre-low pressure compressor water sprayinjection. It is believed that such pre-low pressure compressor waterspray injection provides at least many of the same advantages as theintermediate, or pre-high pressure compressor, spray injection describedabove in connection with FIG. 9.

[0055]FIG. 7 is a schematic illustration of gas turbine engine 200coupled to an electric generator 228. As shown in FIG. 10, engine 200includes a high pressure turbine 230 and a low pressure turbine 232downstream from high pressure compressor 204. High pressure compressor204 and high pressure turbine 230 are coupled via a first shaft 234, andlow pressure compressor 202 and low pressure turbine are coupled via asecond shaft 236. Second shaft 236 also is coupled to generator 228.Engine 200 may, for example, be the LM6000 Gas Turbine Enginecommercially available from General Electric Company, Cincinnati, Ohio,45215, modified to include water spray injection apparatus 206 (FIG. 9).

[0056] Rather than being originally manufactured to include injectionapparatus 206, it is possible that apparatus 206 is retrofitted intoexisting engines. Injection apparatus 206 would be provided in kit formand include tubing 218 and 220, along with water and air manifolds 212and 213 and water metering valve 210. Nozzles 222 and 223 also would beprovided. When it is desired to provide water spray injection, nozzles222 and 223 are installed in outer casing 224 and flow tube 218 isinstalled and extends from eighth stage bleed 214 to air manifold 213.Valve 210 is coupled between a water source and water manifold 212, andwater manifold 212 is coupled to air manifold 213.

[0057]FIG. 8 is a side view of an LM6000 engine 250 of General ElectricCompany modified to include spray injection. Engine 250 includes aninlet 252, a low pressure compressor 254, and front frame 256, and ahigh pressure compressor 258. Engine 250 is modified to include waterspray injection apparatus 260, which includes an air manifold 262 and awater manifold 264 coupled to twenty four radially spaced nozzles 266mounted to an engine outer casing 268. Nozzles 266 spray water intoengine 250 at a location between low pressure compressor 254 and highpressure compressor 258. Injection apparatus 260 also includes aconnector 270 for connecting to an eight stage bleed 272 of highpressure compressor 258, and a pipe 274 extending from connector 270 toair manifold 262. Although not shown in FIG. 8, a heat exchanger (air toair or water to air) may be coupled to pipe 274 to reduce thetemperature of the air supplied to air manifold 262. For illustrationpurposes, nozzles 276 are shown secured to inlet 252 of low pressurecompressor 254. Air and water manifolds also could be coupled to nozzles276 to provide pre-low pressure compressor water spray injection. Thecomponents of injection apparatus 260 described above are fabricatedfrom stainless steel.

[0058] High pressure compressor 258 includes stator vanes whichtypically are not grounded to case 268. When used in combination withwater spray injection, it has been found that grounding at least some ofsuch vanes which come into contact with the water spray may benecessary. To the extent required, and using for example, graphitegrease, such vanes can be grounded to case 268. That is, graphite greasemay be applied to the bearing area of such vanes. For example, suchgraphite grease can be used at the inlet guide vane and for each downstream vane through the second stage. In operation, a portion of thegrease heats and dissipates, and the graphite remains to provide aconductive path from the vane to case 268.

[0059] It also should be understood if the water can be supplied to thewater spray injection nozzles under sufficient pressure, it may not benecessary to supply high pressure air to nozzles. Therefore, it iscontemplated that the eight stage bleed could be eliminated if such highpressure water is available.

[0060]FIG. 9 is a perspective view of connector 270 for connecting eightstage bleed 272 of engine 250. Connector 270 is configured to bethreaded into engagement with engine casing 268 and includes an opening274 normally closed by a bolt 276. When bleed air is desired to beprovided to air manifold 262, bolt 276 is removed and pipe 274 iscoupled to connector 270 using a mating flange at the end of pipe 274that mates with surface 278 of connector 270. Bolt openings 280 enablethe pipe mating flange to be bolted to connector 270.

[0061]FIG. 10 is a cross sectional view of engine 250 and illustratingnozzles 266. Nozzles 266 are configured so that water injected into thegas flow to high pressure compressor 258 provides substantially uniformradial and circumferential temperature reductions at the outlet of highpressure compressor 258. Nozzles 266 include a set 282 of long nozzlesand a set 284 of short nozzles. In the configuration shown in FIG. 10,at least one short nozzle 284 is located at a radially intermediatelocation between two radially aligned long nozzles 282. Short nozzles284 are about flush with the circumference of the flow path and longnozzles 282 extend about four inches into the flow path. Of course,other lengths nozzles may be utilized depending upon the desiredoperation results. In one specific implementation, nozzle 284 extendsabout 0.436 inches into the flow path, and nozzle 282 extends 3.686inches into the flow path. The water ratio between short nozzles 284 andlong nozzles 282 (e.g., 50/50) may also be selected to control theresulting coding at the compressor outlet.

[0062] The temperature sensor for obtaining the temperature at the inletof the high pressure compressor (i.e., temperature T25), is aligned witha long nozzle 282. By aligning such temperature sensor with a longnozzle 282, a more accurate temperature measurement is obtained ratherthan having such sensor aligned with a short nozzle 284.

[0063]FIGS. 11 and 12 illustrate one of nozzles 266. Long and shortnozzles 282 and 284 differ only in length. Nozzle 266 includes a head286 having an air nozzle 288 and a water nozzle 290. Air nozzle 288couples to an air pipe (not shown) which extends from nozzle 288 to airmanifold 262. Water nozzle 290 couples to a water pipe (not shown) whichextends from nozzle 290 to water manifold 264. Nozzle 266 also includesa stem 292 and a mounting flange 294 for mounting nozzle 266 to case262. A mounting portion 296 of stem 292 facilitates engagement of nozzle266 to case 262.

[0064] Stem 292 is formed by an outer tubular conduit 298 and an innertubular conduit 300 located within conduit 298. Air flows into nozzle288 and through the annulus between outer conduit 298 and inner conduit300. Water flows into nozzle 290 and through inner conduit 300. Mixingof the air and water occurs in stem portion 302 formed by a singleconduit 304. An end 306 of nozzle 266 is open so that the water and airmixture can flow out from such end 306 and into the flow path.

[0065]FIG. 13 is a schematic diagram of a control circuit 350 forcontrolling the supply of water and air to nozzles 282 and 284 in engine250 for both frame water injection (aft looking forward) and inlet waterinjection (aft looking forward). As shown in FIG. 13, demineralizedwater is pumped through a motor driven water pump 352. Sensors 354 arecoupled to the water delivery line such as a linear variabledifferential transformer, a pressure sensor, and a water meter valve. Arelief valve 356 is connected in parallel with pump 352, and a flowmeter 358 is coupled in series with pump 352. An air purge line 360 alsois coupled to the water delivery line. Controls 362 for a normallyclosed solenoid valve control 364 air purge operations. A filter 366also is provided in the water delivery line, and sensors 368 with valves370 (manual hand valvelocking flag feature (normally open)) are coupledin parallel with filter 366.

[0066] Normally open valves 372, coupled to controls 374, are providedto enable water to drain from the water delivery line into a water drainsystem. Water in the water delivery line flows through a heat exchanger376 which receives air from the eight stage bleed of high pressurecompressor 258.

[0067] For frame water injection, multiple sensors 378 and controlvalves 380 control the supply of water to nozzles 282 and 284. Circuit350 also includes a water accumulator 382. For inlet water injection,sensors 378 and control valve 384 control the supply of water to nozzles282.

[0068] Letter designations in FIG. 13 have the following meanings.

[0069] T—temperature measurement location

[0070] P—pressure measurement location

[0071] PI—pressure indicator

[0072] N/C—normally closed

[0073] N/O—normally open

[0074] PDSW—pressure differential switch

[0075] PDI—pressure differential indicator

[0076] DRN—drain

[0077] ZS—position switch

[0078] WMV—water metering valve

[0079] PRG—purge

[0080] LVDT—linear variable differential transformer

[0081] In FIG. 13, a solid line is a water supply line, a double dashline is a drain line, and a solid line with has marks is an electricalline. Boxes identify interfaces between the water supply system and theengine. Water metering valves 286 and other control/measurement valves288, and an orifice 290 (for inlet water injection) are utilized inconnection with the control of water flow through circuit 350.

[0082] Set forth below are the controls for various modes of operationof circuit 350 in connection with engine 250. In the description below,the designations Z_SPRINTON, Z_SPRINT, and Z_RAISE have the followingmeaning.

[0083] Z_SPRINTON=System supplier activation/sequence control for offengine H2O delivery.

[0084] Z_SPRINT=Core control logic schedule limit sequence followingheat exchanger purge used for water injection, shutdown, and protectivefunctions.

[0085] Z_RAISE=Z_SPRINT plus the manifold fill timer complete used foralarm functions.

[0086] Also, an * indicates that the selected variable is tunable.

[0087] Pre-Injection Permissives/Purge Activation (AUTO or MANUAL)

[0088] 1. T2>30F*=ON T2<27F*=OFF

[0089] 2. Accumulator charge pressure>40 psig*

[0090] 3. Operator sets Z_SPRINTON to TRUE Heat exchange purge to bypassinitiated

[0091] AUTO At anytime consistent with purge time required

[0092] MANUAL on point of water injection initiation

[0093] 4. Drain valves closed

[0094] Injection Permissives (Pre-Injection Permissives 1-4 Satisfied)

[0095] 1. PS3 50 psi* or less below limit schedule

[0096] 2. T2 regulator not active (MANUAL Only)

[0097] 3. Eight stage air pressure>(PS3/4)

[0098] 4. Heat exchanger purge timer complete

[0099] 5. 8^(th) stage air temperature less than 300 F.*

[0100] 6. Water temperature less than 250 F.*

[0101] MANUAL Mode Sequence

[0102] 1. Operator sets power to satisfy injection permissives 1-2 aboveand sets Z_SPRINTON=T (TRUE=ON)

[0103] 2. Water pump on and heat exchange purge valve to bypass (minimumwater flow).

[0104] 3. Water heat exchanger purge reduce eight stage air temperatureto <300 F. (Five min.*).

[0105] 4. Z-SPRINT=T (TRUE=ON) SPRINT ShutOff valve opens (heatexchanger bypass diverted to engine), minimum scheduled flow to theengine

[0106] 5. Flow fills manifold at minimum scheduled water flow for 60sec.* Z_RAISE=T (TRUE=ON)

[0107] 6. Operator raises SPRINT flow (0.5 gpm/sec) to maximum schedulelevel.

[0108] 7. Operator raises power to desired level or as limited by MW,T3, T48, Ps3, XN25R3, or XN25R.

[0109] 8. Power and water lowered as desired between schedule limits.

[0110] 9. At PS3 60 psi below the base schedule limit sets Z_SPRINT=Fand SPRINT ramp down (−2 gpm /sec) to minimum flow schedule andshutdown.

[0111] 10. Activate Z_SPRINTON to OFF (FALSE=OFF) SPRINT ShutOff valveoff diverts water from engine to bypass, water pump off, heat exchangerpurge valve to bypass, opens the system drains and purges piping untilclear and closes drains.

[0112] AUTO Mode (Permissives Satisfied)

[0113] 1. Operator sets Z_SPRINTON to ON (TRUE=ON) in time to completeheat exchanger purge prior to SPRINT activation permissives.

[0114] 2. Z_SPRINT=T will initiate automatically upon reachingpermissive point.

[0115] 3. SPRINT ShutOff valve opens (diverts water to the engine frombypass)

[0116] 4. Manifold fill on minimum schedule (60 sec.* delay) Z_RAISE=Tthen ramps water (0.5 gpm/sec) to maximum scheduled flow.

[0117] 5. Power ramps to desired level and limited by MW vs. T2 Limiter,T3, T48, Ps3, XN25R3, or XN25R.

[0118] 6. Power lowered as desired to 60 psi* below the base schedulelimit (T_P3BNVG) before SPRINT ramp down (−2 gpm/sec) to minimum flowschedule and shutdown occurs.

[0119] 7. Activate Z-SPRINTON to OFF (FALSE=OFF) SPRINT ShutOff valveoff, heat exchanger purge valve to bypass, water pump off, and open thesystem drains and purge piping until clear.

[0120] Alarm Requirements

[0121] Z_RAISE=TRUE (TRUE=ON) Manifold fill timer satisfied and SPRINTflowing for ALARMS.

[0122] 1. Flow error (Idemand−metered) >3 gpm* for 5 seconds*−Alarm

[0123] 2. 8^(th) stage air temperature >250 F.* for 5 seconds*−Alarm

[0124] Water Shutdown Requirements

[0125] Z_SPRINT=F initiates water shutdown thru ramp down control limitsand activates water shutoff.

[0126] 1. Flow error (demand−metered) >6 gpm* for 10 seconds*−setZ-SPRINT=F

[0127] 2. Pressure loss below 24 psi* at water demand >6 gpm*—setZ_SPRINT=F

[0128] 3. Pressure loss below 50 psi* at water demand >10 gpm*—setZ_SPRINT=F

[0129] 4. 8^(th) stage air temperature greater than 300 F.*—setZ_SPRINT=F

[0130] 5. Eight stage air pressure <(PS3/4)—set Z_SPRINT=F

[0131] 6. T2<27 F.—set Z_SPRINT=F

[0132] 7. PS3 not within 60 psi* of Ps3 limit schedule—set Z_SPRINT=F

[0133] 8. Any gas turbine shutdown, drop load, or step to idle—setZ_SPRINT=F (bypass water ramp down control)

[0134] 9. Circuit breaker not closed—set Z_SPRINT=F (bypass water rampdown control)

[0135]FIG. 14 is a chart illustrating an exemplary water schedule forthe engine arrangement illustrated in FIG. 8, and FIG. 15 is a chartillustrating the output, heat rate, flow, and water supplied to theengine illustrated in FIG. 18 at various ambient temperatures. Theamount of water supplied to the nozzles varies depending, for example,on the ambient temperature as well as the size of the desired droplets.A droplet size of 20 microns has been found, in at least oneapplication, to provide the acceptable results. Of course, the operatingparameters of the engine in which water spray injection is utilized, thedesired operating parameters, and other factors known to those skilledin the art affect the amount of water spray injection.

[0136]FIG. 16 is a chart illustrating the high pressure turbine cavityflow relationship versus the high pressure compressor exit correctedspeed of the engine illustrated in FIG. 18. An additional engine controllimit is used with the engine illustrated in FIG. 8 to protect the highpressure turbine internal cavity temperatures from getting too hot as aresult of ingesting high pressure turbine gas path air. The highpressure turbine cavities are cooled with air from the high pressurecompressor at an adequate flow and pressure level such that there isalways a positive air flow from the internal cavity into the highpressure turbine gas path, hence eliminating the possibility ofingestion. Since the objective of water injection into the compressioncomponents is to cool temperature T3 so the engine can be throttlepushed to increase power, the high pressure system runs faster than itnormally would without the water injection. However, the parasitic airthat is provided by the compressor to cool the turbine cavities isreduced. The curve illustrated in FIG. 19 shows the relationship of highpressure compressor cooling airflow as a function of the high pressurecompressor speed corrected to the high pressure compressor exittemperature. The high pressure compressor exit corrected temperature isdefined as:

HP physical speed * square root (International standard temperature/HPCexit temperature)

[0137] or,

XN25R3=XN25*(T _(STD) /T3)^(½)

[0138] where T_(STD)=518.67⁰R (59⁰ F.).

[0139] As shown in the curve illustrated in FIG. 19, there is a minimumhigh pressure turbine cavity flow required to ensure no high pressureturbine cavity ingestion. This level of flow and its relationship withhigh pressure compressor exit corrected speed define the XN25R3 that theengine must be controlled to as a maximum limit.

[0140] With respect to the droplet size, a minimum drop size at eachflow rate should be produced to both reduce the residence time forcomplete evaporation and to hold drop sizes small enough to preventblade erosion. Set forth below is a manner for analyzing droplet size.More specifically, and for a preliminary analysis, a 3D model of a 30°sector of the LM-6000 booster duct is employed to determine the velocityand temperature field in the duct. No swirl is assumed at the duct inletand the nozzle tips are located in the outer casing at the inlet of thebooster duct aimed radially inward. The nozzle axis was orthogonal tothe outer casing surface and the injection point was about 0.2 in.radially inward from the casing surface. The nozzle generated drop sizevalues were taken to be the smallest values of the RR drop size, givenby Equation 1. Two smaller values (i.e., 10.5 μm and 7.5 μm) were alsoassumed to determine the effect of drop sizes smaller than thosetypically generated by air atomized nozzles. The results are set forthin FIG. 17. It was assumed that 36 nozzles at 0.5 GPM each wereemployed, i.e., 3 to a 30° sector.

Volume Fraction above diameter d=exp−  (1)

[0141] The relation between the water flow at the inlet to the HPcompressor and the stage for complete evaporation is shown in FIG. 18.

[0142] The data in FIG. 18 can be used to determine the approximatemaximum drop size which has to be present at the inlet to the HPcompressor in order to allow complete evaporation at the indicatedstage. The drop sizes obtained are also shown in FIG. 18. Thiscalculation assumes that the average drop size obtained fromre-entrainment at wetted surface is the same as the deposited drop size.Due to the increasing air density and smaller amount of liquid presentin the compressor the actual re-entrained drop sizes will be less thanthose shown in FIG. 18. Although it may seem unnecessary to generatesmaller drops with spray nozzles than those that are generated in thecompressor via re-entrainment, this is not so since the smaller thenozzle generated drops the smaller the fraction of the compressor inletflow rate that deposits on the HP inlet guide vanes. In addition, thefraction of wetted area at stages where wetting was indicated could notbe determined with any accuracy. It is possible, therefore, that lesswater was present in the HP compressor than that implied by the ‘wet’casing temperatures.

[0143] The location for complete evaporation is shown in FIG. 19. Thedata shows that about 20% more water injection can be evaporated at agiven stage than that calculated in the preliminary analysis.

[0144] The same nozzle flow rates and initial drop sizes as those givenin FIG. 19 were located at the inlet to the LP compressor to evaluatethe location of complete evaporation in the HP compressor. The smallerdrop sizes generated by the nozzles cause only a fraction of the nozzleflow to be deposited on the inlet guide vanes of the LP compressor.While the deposited flow behaves the same, the fraction that does notdeposit evaporates more rapidly in the LP compressor and booster duct.

[0145] The method for calculating the evaporation of the water initiallydeposited in the LP compressor is the same as that discussed previously.The evaporation of the fraction in drop form was calculated using amodel that determines the location of complete drop evaporation. Thelatter was located in the LP compressor due to the small cut-off sizefor the undeposited flow. This cut-off size was calculated to be 13 μmat the inlet to the LP using a trajectory analysis. The results for thefirst four nozzles in FIG. 19 are shown in FIG. 20 where a total of 18GPM is again injected initially at 0.5 GPM per nozzle.

[0146] As a calibration for the effect of the drop cut-off size oninitial deposition, if a 13 μm rather than a 10 μm cut-off size isemployed for nozzle 3 in FIG. 20, then complete evaporation would takeplace at the 11^(th) stage rather than the 9-10th stage of the HPcompressor. Compared to injection at the booster duct inlet, somewhatless evaporation takes place in the booster duct due to an increase ofthe average drop size in the booster duct with injection at the LPinlet, while evaporation in the LP compressor results in earlierevaporation in the HP compressor.

[0147] With respect to nozzle selection and performance, the performanceof selected pressure and air atomized nozzles and their effect onevaporation in the HP compressor requires knowledge of the temporal dropsize distribution generated by the nozzles in the environment in whichthey are to be employed. The temporal size distribution has to bemeasured at the air density of interest. The spatial distribution ofdrop size, liquid volume fraction and drop velocity profile needs to bemeasured to calculate the temporal drop size.

[0148] A spray tunnel can be employed to measure the performance of thenozzles. The tunnel, in an exemplary test, is supplied by up to 7 lb/sair at pressures sufficient to match the booster duct air density of0.13 lb/ft.³. The air velocity in the tunnel was varied from 45 to 75ft/s to eliminate reverse circulation of the spray at the outer sprayboundary and to keep the spray diameter small enough to avoid dropimpingement on the quartz windows. The air temperature was kept below95° F. to eliminate the need to account for evaporation between thenozzle and measurement locations.

[0149] The radial distribution of the drop velocities in the axialdirection are obtained from the measurement of the air velocities of therespective atomizing air flow rates but without water flow. The radialvalues of the RR drop size are multiplied by the radial values of theliquid volume fraction and axial drop velocities with the resultingproduct then integrated over the spray radius. After dividing by theintegrated mean liquid volume fraction and axial velocity over the spraycross-section, the mean flowing RR drop size is obtained.

[0150] The air atomized nozzle performance is better than that of thepressure atomized nozzle. At 135 psig, 24 air atomized nozzles at 24 GPMtotal injection allows evaporation in the HP compressor while the 3000psi pressure atomized nozzles cause 5 GPM out of the 24 GPM to breakthrough the HP compressor. In order to evaporate 24 GPM in the HPcompressor with pressure atomized nozzles at 1 GPM per nozzle, at leastsome nozzle configurations would have to be operated at 5000 psi. Atlower water rates per nozzle, the air atomized nozzle performanceimproves while the pressure atomized nozzle performance decreases if thenozzle configuration is not changed. Nozzles are commercially availablefrom EST Woodward, Zeeland, Mich., 49464.

[0151] Again, and in summary, the above described water spray injectionprovides the important result that increased power output can beobtained using the same compressor discharge temperature control limit.That is, by injecting atomized water spray in front of the boosterand/or high pressure compressor, the inlet temperature of the highpressure compressor is significantly reduced. Therefore, using the samecompressor discharge temperature control limit, the high pressurecompressor is able to pump more air, achieving a higher pressure ratio.This results in higher output and improved efficiency. In addition toincreased power output, the above described water spray injectionprovides the advantage of less water consumption as compared tointercooling under the same conditions.

[0152] While the invention has been described in terms of variousspecific embodiments, those skilled in the art will recognize that theinvention can be practiced with modification within the spirit and scopeof the claims.

1. An engine, comprising: a high pressure compressor; and waterinjection apparatus for injecting water into the gas flow at a locationupstream from said high pressure compressor, said water injectionapparatus comprising a plurality of nozzles arranged so that waterinjected into the gas flow by said nozzles results in substantiallyuniformly reducing the temperature of the gas flow at the high pressurecompressor outlet.
 2. An engine in accordance with claim 1 wherein saidnozzles comprise long nozzles and short nozzles, said nozzles arrangedin an alternating configuration so that one of said short nozzles isradially intermediate each pair of said long nozzles.
 3. An engine inaccordance with claim 1 wherein said water injection apparatus furthercomprises a water reservoir in flow communication with each said nozzle,and a water valve for controlling the flow of water from said reservoirto said nozzles.
 4. An engine in accordance with claim 3 furthercomprising a water manifold in flow communication with and intermediatesaid water valve and said nozzles.
 5. An engine in accordance with claim1 further comprising a heating source for atomizing water supplied tosaid nozzles.
 6. An engine in accordance with claim 5 wherein said highpressure compressor comprises a plurality of stages, and said source ofheated air comprises at least one stage of said high pressurecompressor.
 7. An engine in accordance with claim 6 further comprisingan air manifold intermediate said heated air source and said nozzles. 8.An engine in accordance with claim 7 wherein a flow pipe extends fromsaid stage of said high pressure compressor to said air manifold, andsaid water injection apparatus further comprises a heat exchangercoupled to said flow pipe to reduce a temperature of air flowing throughsaid pipe to said air manifold.
 9. An engine in accordance with claim 1further comprising a low pressure compressor and an intercooler inseries flow relationship with said low pressure compressor and said highpressure compressor, said intercooler comprising an inlet coupled tosaid low pressure compressor outlet for receiving at least a portion ofgas flowing from said low pressure compressor outlet, and an outletcoupled to said high pressure compressor inlet.
 10. An engine inaccordance with claim 1 further comprising a combustor locateddownstream of said high pressure compressor.
 11. An engine in accordancewith claim 10 further comprising a high pressure turbine and a lowpressure turbine downstream of said combustor.
 12. An engine inaccordance with claim 11 wherein said high pressure compressor and saidhigh pressure turbine are coupled via a first shaft, and said lowpressure compressor and said low pressure turbine are coupled via asecond shaft.
 13. An engine in accordance with claim 1 wherein said lowpressure compressor comprises at least five stages, and said highpressure compressor comprises at least fourteen stages.
 14. An engine inaccordance with claim 13 further comprising a high pressure turbinecomprising at least two stages and a low pressure compressor comprisingat least five stages.
 15. An engine in accordance with claim 1 whereinsaid water injection apparatus further comprises a water reservoir inflow communication with each said nozzle, and a water valve forcontrolling the flow of water from said reservoir to said nozzles. 16.An engine in accordance with claim 1 further comprising a low pressurecompressor and wherein said nozzles are positioned intermediate said lowpressure compressor and said high pressure compressor.
 17. An engine inaccordance with claim 1 further comprising a low pressure compressor andwherein said nozzles are positioned upstream from said low pressurecompressor.
 18. An engine in accordance with claim 1 wherein said highpressure compressor comprises a plurality of stators, said statorselectrically grounded.
 19. An engine in accordance with claim 1 whereineach of said nozzles comprises an inner flow path and an outer flowpath, said inner flow path coupled to a water reservoir, and said outerflow path coupled to a source of heated air.
 20. An engine in accordancewith claim 1 wherein water at said nozzle is under sufficient pressureto atomize.
 21. An engine in accordance with claim 20 wherein waterdroplets from said nozzle have a diameter of about 20 microns.
 22. Anengine, comprising: a low pressure compressor; a high pressurecompressor downstream of said low pressure compressor; a combustorlocated downstream of said high pressure compressor; a high pressureturbine downstream of said combustor; a low pressure turbine downstreamof said high pressure turbine; and water injection apparatus forinjecting water into the gas flow at a location upstream from said highpressure compressor, said water injection apparatus comprising aplurality of nozzles, a water reservoir in flow communication with eachsaid nozzle, and a water valve for controlling the flow of water fromsaid reservoir to said nozzles, said nozzles arranged so that waterinjected into the gas flow by said nozzles results in substantiallyuniformly reducing the temperature of the gas flow at the high pressurecompressor outlet.
 23. An engine in accordance with claim 22 whereinsaid nozzles comprise long nozzles and short nozzles, said nozzlesarranged in an alternating configuration so that one of said shortnozzles is radially intermediate each pair of said long nozzles.
 24. Anengine in accordance with claim 22 wherein said high pressure compressorcomprises a plurality of stages, and said water injection apparatuscomprises a flow pipe extending from one of said stages of said highpressure compressor to supply heated air to said nozzles, said waterinjection apparatus further comprising a heat exchanger coupled to saidflow pipe to reduce a temperature of air flowing through said pipe tosaid air manifold.
 25. An engine in accordance with claim 22 furthercomprising an intercooler in series flow relationship with said lowpressure compressor and said high pressure compressor, said intercoolercomprising an inlet coupled to said low pressure compressor outlet forreceiving at least a portion of gas flowing from said low pressurecompressor outlet, and an outlet coupled to said high pressurecompressor inlet.
 26. An engine in accordance with claim 22 wherein saidhigh pressure compressor and said high pressure turbine are coupled viaa first shaft, and said low pressure compressor and said low pressureturbine are coupled via a second shaft.
 27. An engine in accordance withclaim 22 wherein said low pressure compressor comprises at least fivestages, said high pressure compressor comprises at least fourteenstages, said high pressure turbine comprising at least two stages, andsaid low pressure compressor comprising at least five stages.
 28. Anengine in accordance with claim 22 wherein said nozzles are positionedintermediate said low pressure compressor and said high pressurecompressor.
 29. An engine in accordance with claim 22 wherein saidnozzles are positioned upstream from said low pressure compressor. 30.An engine in accordance with claim 22 wherein said high pressurecompressor comprises a plurality of stators, said stators electricallygrounded.
 31. An engine in accordance with claim 22 wherein each of saidnozzles comprises an inner flow path and an outer flow path, said innerflow path coupled to a water reservoir, and said outer flow path coupledto a source of heated air.
 32. An engine in accordance with claim 22wherein water at said nozzle is under sufficient pressure to atomize.33. An engine in accordance with claim 32 wherein water droplets fromsaid nozzle have a diameter of about 20 microns.
 34. Water injectionapparatus for injecting water into the gas flow of an engine including ahigh pressure compressor, said apparatus comprising a plurality ofnozzles configured to be secured to the engine upstream of the highpressure compressor so that water injected into the gas flow by saidnozzles results in substantially uniformly reducing the temperature ofthe gas flow at the high pressure compressor outlet.
 35. Water injectionapparatus in accordance with claim 34 wherein said nozzles comprise longnozzles and short nozzles, said nozzles configured to be arranged in analternating configuration so that one of said short nozzles is radiallyintermediate each pair of said long nozzles when secured to the engine.36. Water injection apparatus in accordance with claim 1 furthercomprising a water reservoir for being in flow communication with eachsaid nozzle, and a water valve for controlling the flow of water fromsaid reservoir to said nozzles.
 37. Water injection apparatus inaccordance with claim 36 further comprising a water manifold configuredto be in flow communication with and intermediate said water valve andsaid nozzles.
 38. Water injection apparatus in accordance with claim 34further comprising an air manifold and a flow pipe configured to extendfrom a stage of the high pressure compressor to said air manifold. 39.Water injection apparatus in accordance with claim 38 further comprisinga heat exchanger configured to be coupled to said flow pipe to reduce atemperature of air flowing through said pipe to said air manifold. 40.Water injection apparatus further comprising an intercooler configuredto be in series flow relationship with a low pressure compressor of theengine and the high pressure compressor.
 41. Water injection apparatusin accordance with claim 34 wherein said nozzles are configured to bepositioned intermediate a low pressure compressor of the engine and saidhigh pressure compressor.
 42. Water injection apparatus in accordancewith claim 34 wherein said nozzles are configured to be positionedupstream from a low pressure compressor of the engine.
 43. Waterinjection apparatus in accordance with claim 34 wherein each of saidnozzles comprises an inner flow path and an outer flow path, said innerflow path configured to be coupled to a water reservoir, and said outerflow path configured to be coupled to a source of heated air.
 44. Amethod for operating a gas turbine engine including a high pressurecompressor and a water injection apparatus for injecting water into agas flow of the engine upstream of the high pressure compressor, saidmethod comprising the steps of: operating the engine without injectingwater into the gas flow of the engine; and once about full power isreached without injecting water into the gas flow, activating the waterinjection apparatus to inject water into the gas flow.
 45. A method inaccordance with claim 44 wherein the water injection apparatus includesa water valve, and wherein activating the water injection apparatus toinject water into the gas flow comprises the step of opening the watervalve.
 46. A method in accordance with claim 44 wherein the engineincludes a low pressure compressor, and the water injection apparatusincludes a plurality of nozzles, said nozzles positioned intermediatethe low pressure compressor and the high pressure compressor.
 47. Amethod in accordance with claim 44 wherein the engine includes a lowpressure compressor, and the water injection apparatus includes aplurality of nozzles, said nozzles positioned upstream from the lowpressure compressor.
 48. A method in accordance with claim 44 whereinafter activating the water injection apparatus to inject water into thegas flow, said method further comprises the step of increasing fuel flowto the engine combustor.